An operator of a mobile telecommunication network such as a Global System for Mobile communication (GSM) or a Universal Mobile Telecommunication System (UMTS) uses USSD which stands for Unstructured Supplementary Service Data (hereinafter referred to as Service Data) for a variety of services, often related to pre-paid. Examples of these services are credit replenishment, credit inquiry and call information inquiry.
Service Data may also be used in combination with other services, such as a Virtual Private Network (VPN). Service Data may be used as mechanism to trigger stand-alone services, such as location request, weather report, and traffic report. One of the advantages of sending an service request using Service Data is that it is generally faster than sending a short message service message (SMS).
Service Data services are offered by a Service Data handler (hereinafter referred to as USSD Handler), which is the service logic that provides the service to the user. The USSD Handler may be located in the Home Location Register (HLR) or external to the HLR, e.g. in a service control point (SCP).
The communication between the HLR and the external Service Data Service may run via a Service Data signalling gateway. Operators may have a need to charge the user for the use of particular Service Data services. In addition, some operators require that the charge of the use of Service Data services is based on the location of the subscriber. Location based charging for Service Data services may also be a regulatory requirement in certain countries.
Operators may also need to apply differentiated tariff schemes on the use of Service Data services, based on the time of day the subscriber is using these services.
For example during off-peak hours, the tariff may be lower than during peak hours, when the load on the Network is at its highest. Considering that in one country or serviced area of a network different time-zones may occur, an operator may need to know at what local time of day (hereinafter called “Local Time”) the subscriber is using the service.
Besides charging of Service Data services, an operator or service provider may need to provide services to a subscriber, based on the location of the subscriber. These kind of services comprise stand-alone services as mentioned before, such as location request, weather report, traffic report, and other services that are typically location dependent or location oriented.
Determining subscriber's geographical location, according to the state of the art, takes place in the following way.
When the subscriber initiates a Service Data session, the HLR has the visitor location register (VLR) address available; the VLR address gives an indication of the location of the subscriber. The VLR address may be used to adapt the charge towards the subscriber for the Service Data service. For some operators, however, the VLR address is not accurate enough for this purpose. Especially when the VLR service area spans a large geographical area. Instead of the VLR address, the operator may need to know the current cell identifier (Cell ID) or location area. In addition, for charging reasons, the location of a subscriber is often defined by the location number.
A location number is derived from the Cell ID where the subscriber is located. Location number, Cell ID and location area may be known in VLR, but not in the HLR. Hence, a USSD Handler (residing in HLR or external to HLR) does not have access to that information at the time that the Service Data Service is invoked. Location based charging of the Service Data service is therefore not possible.
In some solutions of the prior art, location information indicating means in a mobile station (MS) are adapted to identify a cell identifier for a cell within the digital cellular communication network where the mobile station is roaming and also to output the cell identifier via the unstructured supplementary service data interface means. However, this solution has a number of disadvantages.
Firstly this is a complex solution, requiring special and dedicated location information Service Data messages, which also increases traffic. It also requires additional complexity in the Mobile Station. The current prior art solutions describe a method whereby a mobile station uses a dedicated mechanism to send Location Information via a Service Data message to a service.
Secondly, a Mobile Services Switching Centre (MSC) may service a wide area consisting of cells that cover possibly more than one time zone. There is a need for a reliable solution for determining the use of a service or the Service Data service itself, by the subscriber at a particular local time of day. The current solutions only provide the time of receiving of a request, being the local time of a MSC receiving the request, to be forwarded by a dedicated Service Data message.